1. Related Field
The present patent application generally relates to serial storage architecture (or xe2x80x9cSSAxe2x80x9d) storage subsystems and, more particularly, to a SSA storage subsystem having a SSA initiator and an intelligent backplane configured for the exchange of status and control information with the SSA initiator.
2. Description of Related Art
Presently, many storage subsystems are based upon small computer systems interface (or xe2x80x9cSCSIxe2x80x9d) architecture. Recently, however, considerable attention has been directed towards the development of storage subsystems based upon SSA Generally, SSA-based storage subsystems are capable of providing higher level of performance, fault tolerance, data availability and connectivity than is possible with similar SCSI-based storage subsystems. SSA-based storage subsystems also offer reduced interface costs. For example, SSA-based storage subsystems require no address switches and no discrete terminators.
SSA-based storage subsystems are arranged into a serial string of up to 128 devices, the ends of which are often connected to form a loop. Generally, such strings include an SSA initiator and any number of SSA targets, most commonly, storage devices such as drives, which execute commands received from the SSA initiator, mounted in drive bays. Each of the devices included in a string or loop has first and second full duplex ports.
Each device in an SSA-based storage system is sequentially addressed based upon its location within the string. If a device is added or removed from the string, a number of the other devices in the string will require re-addressing. While this ability to dynamically re-address devices has eliminated the need for user configurable jumpers, it is often difficult to spatially locate a particular device within a large storage subsystem based upon a machine assigned numerical address. Specifically, when in the storage subsystem, the string bypasses selected drives within a drive pod or is comprised of drives installed in plural drive pods. Thus, the task of locating and replacing a failed drive often proves unnecessarily complicated. Accordingly, there is often the need to communicate physical information regarding the drives of the string.
SSA storage subsystems have yet to satisfy this need. LEDs physically installed at each drive may convey information regarding drive activity and/or status but cannot be used for remote monitoring and control. Alternately, while it is possible to install a separate communication path for remote monitoring and control, such a solution would be quite burdensome.
It can be readily seen from the foregoing that it would be desirable to provide an SSA storage subsystem in which status and control information may be exchanged between the SSA initiator and the physical location where the storage devices included in the SSA storage subsystem are installed. It is, therefore, the object of this invention to provide such an SSA storage subsystem.
A serial storage architecture (SSA) storage subsystem includes a backplane, first and second storage devices connected to the backplane, an SSA initiator and a plurality of SSA targets, which include the backplane of the storage pod and the first and second storage devices, serially connected to the SSA initiator. In various aspects thereof, a controller and at least one status and/or control register may be provided on the backplane. Each status register indicates the status of an operating parameter of the storage devices coupled thereto. To report the occurrence of an event related to one of the operating parameters, the controller polls the status registers and, based upon the state thereof, the controller will determine whether to issue a notification to the SSA initiator. Each control register transmits control signals to the storage devices in response to instructions issued by the SSA initiator. Preferably, each status register includes a status bit corresponding to each storage device and each control register includes a control bit corresponding to each storage device. The occurrence of an event at a storage device related to an operating parameter is indicated if a status bit of the status register corresponding to the operating parameter undergoes a state change. Conversely, by asserting a selected control bit, the corresponding storage device will execute an instruction issued by the SSA initiator by enabling a control line which causes an activity to occur.
In various aspects thereof, the status registers may include a device present register for indicating the presence of a storage device within a drive bay, a device fault register for indicating the occurrence of a fault by the storage device and a drive write protect register for indicating whether the storage device is write protected. The control registers, on the other hand, may include a bay power control register for controlling power to the storage devices and a device write protect register for switching the storage device into or out of write protect mode.
In other aspects thereof, additional status and/or control capability may be provided to the backplane. In one such aspect, the backplane may include a thermal monitoring system for determining an internal operating temperature for a storage pod which houses the first and second storage devices. By analyzing thermal information polled thereby, the controller may determine the occurrence of thermal events. In another such aspect, the backplane may include a voltage monitoring system for determining voltage level for power supplied to the storage pod. By analyzing power information polled thereby, the controller may determine the occurrence of power events. In yet another such aspect, the backplane may include a fan speed register. By analyzing fan speed, the controller may determine the occurrence of fan speed events. In one further such aspect, a control panel for displaying messages from the SSA initiator may also be provided.